There are probably others, but this is the best known by which the Anglo-Saxon Englisc Fyrdsmen (militia), Thegns (NCOs) and Huscarls (Officers) would swear their oath to fight for their King or Lords;

“I swear before this company that I shall fight to the death for my King. If my King or my Lord shall die, I shall take his place and fight as he would have fought. If any man here see me taken with weak heart and run away he shall remind me of this pledge made here before my kin.”

Such was the oath that saw the most loyal, the Huscarls, die to a man upon Senlac Hill even after King Harold had fallen.